The present invention relates to an improved valve system for controlling fluid flow through multiple conduits and, in particular, to a safety valve for use in the administration of medical fluids to patients.
Medical procedures often require introducing fluids into a patient using systems such as parenteral administration sets. Many of these administration sets include multiple, independently operated clamps or valves that control the flow of fluids through the administration set and into the patient. Such sets generally include a vent conduit and at least one supply conduit connected to a supply container such as a fluid-filled bag. To dispense the fluid, a medical operator or other user manually employs the clamps as needed to close or open the conduits of the administration set during the fluid administration. These administration sets may also include injection ports to introduce additives such as antibiotics or other medicaments into the administration solution, as required.
In one medical application, an administration set is used to continuously feed a steady and continuing flow of saline, dextrose or other solution from the supply container intravenously to the patient. The amount fed is limited by the amount in the supply container. In other medical procedures, a precise volume less than the total supply container volume must be fed to the patient over a single flow period. For this volumetric use, the administration set may include a burette chamber in the flow path that may be used to more precisely measure a prescribed volume of solution. In this arrangement, the solution flows from the supply container to the burette chamber to be measured and then to the patient. Depending on the means used to cause the fluid to flow downstream to the patient, an intermediate chamber, such as a drip chamber, may be placed in the flow path downstream of the burette chamber so that fluid flow may be monitored and timed.
In the use of administration sets, it is typical to prime the set before use to eliminate any air that may be harmful to the patient. The valves and clamps of the administration set, including any associated with the burette chamber, must be activated appropriately to assist in entering the priming mode of the administration set. In the priming mode, fluid from the supply container is channeled into the calibrated burette chamber. Typically, individual conduit clamps of the burette chamber are separately manipulated so that both vent and supply conduits are open which allows the source fluid to flow into the burette chamber and to vent the displaced air out the vent conduit. Another clamp may then be used to prime the rest of the administration set conduits and to control the fluid flow through the system.
Once primed, the operator may place the administration set having a burette chamber into the intermittent flow mode which delivers only the medical fluid in the burette chamber to the patient by releasing the vent conduit and closing the supply conduit. The precise amount of fluid that has been measured by the operator with the burette chamber is then administered to the patient. Alternately, the operator may place the administration set into a continuous flow mode by opening the supply conduit to the desired flow level and closing the vent conduit so that the flow of fluid from the supply container is continuous.
Burette chambers typically have an upstream supply conduit through which fluid from a supply source flows into the burette chamber. Burette chambers also typically have an upstream vent conduit through which air in the burette chamber may be vented to the outside as the chamber is filled with fluid from the supply source. Both of these upstream conduits may be clamped shut or may be opened as needed for the flow mode desired. As described above, many administration sets having a burette chamber providing for the priming mode, intermittent flow mode, and continuous flow mode require a particular arrangement of conduit clamps to close or open the upstream vent and supply conduits. These arrangements can become troublesome and inconvenient to an operator. It is necessary for the operator to remember which valve or valves must be open and which must be closed for the particular flow mode desired. Failure to correctly set the valves can result in another mode being configured rather than the one desired.
An effective medical burette administration set must be designed for safety and ease of operation. Preferably, the set includes a safety system that would prevent both upstream conduits (supply and vent conduits) from being simultaneously closed, known as a xe2x80x9cclosed-closedxe2x80x9d flow mode. Such a condition could result in a partial vacuum being formed in the administration set and the burette chamber that could potentially slow or interrupt fluid delivery to the patient or in a worse case, pull blood from the patient""s catheter subsequent to the set being removed from an infusion pump. Drawing blood from the catheter presents a risk to the patient of possible clotting or damage to the vessel in the region of the catheter tip. A preferred design would also take measures to avoid contamination to the operator, such as smooth design features that do not tear gloves worn by the operator. Additionally, a preferred design would include unambiguous visual indicators used to gage the flow configuration of the system. These indicators minimize the risk of accidental placement of the administration set into an inadvertent operating state. Known administration sets have certain design limitations that have not entirely overcome these concerns.
U.S. Pat. No. 5,853,398 to Lal et al. proposes a flow-adjusting clamp system in a burette administration set to select the described flow modes and avoid the xe2x80x9cclosed-closedxe2x80x9d flow mode. In the Lal system, a dual-slotted cam mounted at the input end of the burette functions as a selective clamp by closing off flow alternately through the two flexible conduits running through each slot of the cam. One conduit is a vent conduit while the other is a conduit from the fluid reservoir. The slots in the cam vary between a narrow opening and a wide opening. The narrow opening is used for closing off or occlusion of the conduit while the wide opening is used for unrestricted flow. The medical operator grasps the edge of the cam to manually pivot the cam to a selected rotational position. As the cam pivots horizontally, the vertical conduits slide laterally along the open unrestrictive portions and the closing portions of the slots. The edges of the narrow portions of the slots close off flow through the conduits. The wider portions of the slots release flow through the conduits. The slots are aligned so that at any cam position, both slots will not be closed simultaneously as long as the conduits remain in the vertical position. While the medical operator pivots the dual slotted cam through a predetermined arc, the edges of the slots restrict and release the vent and supply conduits to select the priming, intermittent and continuous flow modes.
Administrative sets that use a horizontal dual-slotted cam system potentially introduce operational problems to medical personnel. In order to accurately control flow, the conduits must remain vertically fixed while laterally sliding along the slots to maintain the same rotational position. Below the pivoting cam, the conduits are held in a substantially fixed position by their connections to the burette cap. However, above the pivoting cam, the system does not restrict movement of the flexible conduits which potentially allow the conduits to move from the vertical position. If the pivoting cam is not mounted close enough to the burette cap and if the conduits move from a vertical position such as by bending in response to the narrow slots of the slotted cam, the narrow portion of a cam slot may not fully engage the conduit and full occlusion may not occur. The medical operator may have to manually arrange the conduits in the cam slots or hold the conduits steady while the cam is rotated to correct the flow mode. Arranging the conduit while pivoting the dual-slotted cam could prove difficult to a medical operator wearing protective gloves. The medical operator could potentially tear the gloves while trying to orient the cam and conduits in the correct alignment. Moreover, the medical operator could err in the placement of the conduits within the cam and apply an inadvertent flow mode. Introducing this possible need for manual control into use of the cam is undesirable.
Additional complications may arise in using this system due to the difficulty in reading the operating state or flow mode of the system from a distance. To accurately determine the operating state of the system, the medical operator or other personnel must see the location of the conduits within the dual-slotted cam. Since the cam is horizontally located on top of the burette cap, a medical operator would have to look down on the system from a close distance to read the operating state. This arrangement makes it more difficult to use and less versatile.
Hence those skilled in the art have recognized a need for an improved burette administration set. Another need recognized is for a safety valve capable of placing a burette fluid administration set in the priming, intermittent, and continuous flow modes while avoiding the xe2x80x9cclosed-closedxe2x80x9d flow mode. Such a system should restrict the movement of the conduits to avoid inadvertent operating states of the system. The system should also be relatively easy to use by providing a single control element that is readily visible and assessable to the medical operator. Additional visual indicators should be provided to allow the medical operator to view the operating state of the system from a distance. The invention fulfills these needs and others.
The invention in one aspect is directed to a system for controlling fluid flow through multiple conduits. The system comprises a housing in which the conduits are held in predetermined, fixed positions, a cam rotatably disposed within the housing and mounted so as to permit controlled, alternate compression contact of an external surface of the cam with each of the conduits to restrict flow therein, and a control element operably connected to the cam to selectively position the cam into contact with each of the conduits, wherein the housing secures the conduits against movement at positions both above and below the contact locations of the cam with the conduits.
In more detailed aspects, the cam is mounted so that it rotates about an axis that is perpendicular to longitudinal axes of the conduits. The housing receives the conduits so that the housing provides support for each conduit generally surrounding the area of compression contact with the cam. The cam is located between the conduits. The housing comprises a stop surface that is located to prevent the cam from rotating through a predetermined arc. The housing comprises a visual indicator visible from a position external to the housing to disclose the position of the cam in relation to the conduits.
In yet further aspects, the control element comprises a handle disposed on the outside of the housing, the handle aligned with the cam in a predetermined manner to indicate the position of the cam. The handle is aligned with the cam to indicate a flow operating state of a conduit. The handle is aligned with the cam to indicate that a conduit is occluded. An indicator is disposed on the outside of the housing so that aligning the handle with the indicator discloses a flow operating state of a conduit.
In other detailed aspects, the system further comprises a positioning device located within the housing for controllably holding the cam at a predetermined position. The positioning device comprises a detent. The positioning device further comprises a spring-loaded aligning device located on one of the cam or the housing and the detent is located on the other of the cam or the housing. The spring-loaded aligning device comprises a ball bearing, and a spring, the spring located so as to urge the ball bearing into the detent so that the cam will controllably remain in a predetermined position at the detent. In a further aspect, the system comprises a plurality of positioning devices located within the housing for controllably holding the cam at predetermined positions in relation to the conduits.
In more detailed aspects, the cam is solid. The cam rotates about an axis located parallel to longitudinal axes of the conduits.
In accordance with other aspects, the invention is directed to a medical burette having an upstream end and a downstream end interconnected by a burette chamber, the burette chamber having a longitudinal axis, the burette comprises a housing disposed at the upstream end of the burette, the housing having a vent conduit, and a supply conduit, the conduits held in fixed positions within the housing and in fluid communication with the chamber, a cam rotatably mounted within the housing between the vent conduit and the supply conduit, the cam mounted within compression contact range of both the conduits such that the cam may selectively be rotated to occlude either of the conduits, a control element connected to the cam for rotating the cam to selectively occlude the conduits, and the control element connected to the cam such that the control element has an indicator function of the position of the cam in regard to the occlusion of the conduits.
In more detailed aspects related to the burette, the cam is mounted so that it rotates about an axis that is perpendicular to longitudinal axes of the conduits. The housing receives the conduits so that the housing provides support for each conduit generally surrounding the area of compression contact with the cam. The housing comprises a stop surface located to prevent the cam from rotating through a predetermined arc. A positioning device is located within the housing for controllably holding the cam at a predetermined position in relation to a conduit. The positioning device comprises a detent. The positioning device further comprises a spring-loaded aligning device located on one of the cam or the housing and the detent is located on the other of the cam or the housing. The spring-loaded aligning device comprises a ball bearing, and a spring, the spring located so as to urge the ball bearing into the detent so that the cam will controllably remain in a predetermined position at the detent. In yet further aspects, the medical burette further comprising a plurality of positioning devices located within the housing for controllably holding the cam at predetermined positions in relation to the conduits.
In more detailed aspects, the cam is solid. The cam rotates about an axis located parallel to longitudinal axes of the conduits. The cam is mounted so that it may be rotated to a position at which neither conduit is occluded. The burette further comprises indicators at an exterior surface of the housing, the indicators adapted to signal a state of fluid flow of the burette.
In accordance with aspects of a method in accordance with the invention, there is provided a method for controlling fluid flow through multiple conduits into a burette, the burette having a housing disposed at an upstream end, the method comprising positioning the conduits in spaced-apart, fixed positions in the housing, rotating a cam disposed within the housing into compressive contact of an external surface of the cam with each of the conduits to restrict flow therein, and controlling the rotation of the cam with an external control element, and securing the conduits against movement at positions both above and below the contact locations of the cam with the conduits.
In more detailed aspects, rotating the cam comprises rotating the cam about an axis that is perpendicular to longitudinal axes of the conduits. Positioning the conduits comprises locating the conduits in the housing so that housing provides support for each conduit generally surrounding the area of compression contact with the cam. The method further comprises the step of controllably holding the cam at a selected position such that inadvertent rotation of the cam from the selected position is resisted. Holding the cam comprises locating a positioning device partially within the housing and partially within the cam such that rotation of the cam is resisted. The method also comprises in a more detailed aspect biasing the positioning device into the location partially within the housing and partially within the cam. Rotating the cam comprises rotating the cam about an axis that is parallel to longitudinal axes of the conduits.
A more detailed aspect in accordance with the method of the invention includes indicating at an exterior surface of the housing the state of fluid flow of the burette.
Other features and advantages of the invention will become more apparent from the following detailed description of preferred embodiments of the invention, when taken in conjunction with the accompanying exemplary drawings.